These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Megas in Valis II for the Sharp X68000 and MSX 2, unlike than his Alas, Poor Villain-y counterparts in other versions of the game. He's said to have killed his entire family, "including the women and children", his own underlings, and even the monsters who unsealed him. Late in the game, he holds Valia hostage, ordering Yuko not only to surrender, but to strip. Then, when Yuko complies, he kills Valia anyway, by impaling her with his arm, in a bloody mess. After Yuko defeats him, he dies giving her a This Cannot Be! speech, with no empire or minions left to care.
I Am Not Shazam: The heroine's name is Yuko, not Valis, in case you did not know.
That One Boss: The third game, the boss of the first level after finding Nazetti. Raining boulders, an attack that goes across the whole screen, and, of course, an absurd amount of health.
In the first game, the Twin-headed lightning dragon boss gets annoying really fast due to the lightning spell. And then you fight Reiko, who can take away 48% of your health in a single spell cast (said spell is considerably weaker in your hands). The only way to dodge it is with a frame-perfect spell casting. The Final Boss is much easier due to not having a spell that hits the entire screen.